Support PSSE GIC format

[bluejuniper]

Use PSSE GIC format instead of JSON mods file. This would require constructing the DC network JIT instead of in advance, so this would be a pretty big change. PowerWorld Simulator 23 now supports export into this format. Example of PSSE GIC V4 Format for the B4GIC case:

GICFILEVRSN=4
1,'Sub A',0, 40.0000,-89.0000,   0.200,'',''
2,'Sub B',0, 40.0000,-87.0000,   0.200,'',''
0 / End of Substation data, Begin Bus Substation Data
1,1
2,2
3,1
4,2
0 / End of Bus Substation Data, Begin Transformer Data
1,3,0,' 1',  0.0000,  0.0000,  0.0000,0,0,0,'YNd0        ', 1,  1.1000,0,0,0,0
2,4,0,' 1',  0.0000,  0.0000,  0.0000,0,0,0,'YNd0        ', 1,  1.1000,0,0,0,0
0 / End of Transformer Data, Begin Bus Fixed Shunt Data
0 / End of Bus Fixed Shunt Data, Begin Branch Data
1,2,' 1',0, , ,0,0
0 / End of Branch Data, Begin User Earth Model Data
0 / End of User Earth Model Data
0  / End of Switched Shunt Data
0  / End of DC line Data
0  / End of VSC Data
0  / End of Multi-Terminal DC Data
0  / End of FACTS Data
0  / End of Load Data
Q